JP4717472B2 - Substrate polishing method - Google Patents

Description

  The present invention relates to a substrate polishing method for polishing a substrate surface by a CMP method, and more particularly to a substrate polishing method suitable for efficiently polishing a large number of substrates.

  In the manufacturing process of a semiconductor integrated circuit, a semiconductor wafer polishing apparatus using a chemical mechanical polishing (CMP) method is widely used to accurately planarize the surface of a thin film layer. According to this method, it is possible to obtain good flatness particularly on the surface of the interlayer insulating film made of an oxide film, and the yield of products is greatly improved.

  However, in the CMP method, there is a problem that the state of consumable members such as a polishing pad and an abrasive (slurry) and the state of a polishing head for holding a wafer greatly affect characteristics such as a polishing rate and a polishing distribution. . In addition, the semiconductor wafer to be polished has a problem that not only the state of the oxide film formed but also factors such as the device structure and pattern layout affect the finish after polishing.

  In order to eliminate such influence as much as possible, before polishing a device wafer (hereinafter referred to as a product wafer) to be commercialized, the monitor wafer is polished and the polishing rate is measured. A method of empirically determining a polishing condition for a product wafer with reference to a measurement result is generally employed.

FIG. 12 is a flowchart showing an example of a conventional procedure for polishing a semiconductor wafer by the CMP method.
[Step S1] First, using a polishing apparatus in which members such as the same platen and head as the product wafer are polished is set, the monitor wafer having the same material as the polishing target portion of the product wafer is polished. Then, the film thickness before and after polishing is measured, and the polishing rate is calculated from the result. As a result, it is possible to grasp variations caused by consumables such as pads and slurries, the assembled state of members, and the like.

[Step S2] A pilot wafer is extracted from a product wafer on which a predetermined pattern is formed, and the pilot wafer is polished. Since a wafer with a pattern requires less polishing time than when there is no pattern, the polishing time is adjusted based on the polishing rate obtained from the monitor wafer. Then, a deviation from the target film thickness is obtained from the measurement result of the film thickness before and after the polishing, and a polishing time in consideration of this deviation is newly obtained.

[Step S3] The product wafer is polished for the polishing time determined from the polishing result of the pilot wafer.
In this step, for example, the polishing rate is calculated using the monitor wafer about once a day. Each time a predetermined number of polishing processes are performed on the same type of product wafer, the polishing rate is calculated using the pilot wafer. For example, after polishing another type of product wafer, the polishing rate using the pilot wafer is calculated before polishing the next type of product wafer.

  By performing the polishing in the above procedure, the polishing time can be accurately obtained under conditions close to the polishing of the product wafer, and the polishing accuracy of the product wafer is improved. However, such a process takes time and labor, and the production efficiency is a problem.

  For such problems, the polishing shift amount from the reference wafer is obtained in advance as a specific polishing parameter for each product type or process of the product wafer, and the polishing ability of the apparatus is appropriately measured using the reference wafer to obtain the polishing ability. There is a semiconductor wafer polishing method in which the product wafer polishing time is accurately calculated from the specific polishing parameters (see, for example, Patent Document 1).

In addition, the ratio between the polishing rate of the product wafer and the polishing rate of the monitor wafer is obtained at a plurality of points in the production period, and the current ratio is estimated based on a record of the change over time of the product wafer. There is also a production method of a semiconductor integrated circuit in which the polishing conditions are set (see, for example, Patent Document 2).
Japanese Unexamined Patent Publication No. 2004-47747 (paragraph numbers [0014] to [0031], FIG. 1) JP 2004-79728 A (paragraph numbers [0029] to [0046], FIG. 2)

  However, the manufacturing process of semiconductor integrated circuits is required to further improve the efficiency, speed, and cost of the work, and it is necessary to carry out the polishing process for monitor wafers and pilot wafers as much as possible. Therefore, there has been a demand for a technique capable of more accurately calculating the polishing conditions and performing highly accurate polishing.

  The present invention has been made in view of these points, and an object of the present invention is to provide a substrate polishing method capable of high-precision polishing while suppressing work man-hours and material costs.

  In the present invention, in order to solve the above problem, as shown in FIG. 1, in a substrate polishing method for polishing a substrate surface by a CMP method, a polishing rate Rmn using a blank substrate on which the same film material as that to be polished is formed. A first determination step (S102) for determining whether the measurement interval has been exceeded, a second determination step (S105) for determining abnormality of the polishing rate Rmn based on the measurement history of the polishing rate Rmn, and a predetermined substrate. A third determination step (S106) for determining an abnormality in the history of the polishing parameter based on the polishing rate Rmn for polishing to a thickness of, and a predicted value of the polishing parameter is calculated based on the history of the polishing parameter. A predicted value calculating step (S107), and a polishing step (S108) for polishing the substrate by CMP using the predicted value. Substrate polishing method according to is provided.

  In such a semiconductor wafer polishing method, for example, in the first determination step (S102), it is determined that the measurement interval of the polishing rate Rmn using the blank substrate on which the same film material as the object to be polished is exceeded, When the measurement interval exceeds the predetermined time, in the second determination step (S105), an abnormality of the polishing rate Rmn is determined based on the measurement history of the polishing rate Rmn, and further, the polishing rate Rmn is determined to be normal. In this case, in the third determination step (S106), it is determined whether the polishing parameter history is abnormal based on the polishing rate Rmn for polishing the substrate to a predetermined thickness, and the polishing parameter history is determined to be normal. In this case, in the predicted value calculation step (S107), a predicted value of the polishing parameter is calculated based on the history of the polishing parameter, and in the polishing step (S108). Substrate using the calculated predicted value (such as the product to become wafer) is polished by CMP. By such a process, when the transition of the polishing rate Rmn is stable and the transition of the polishing parameter of the substrate based on the polishing rate Rmn is stable, the test polishing using the blank substrate or the substrate to be polished The substrate is polished by predicting the polishing parameters without performing the test polishing using the pilot wafer extracted from the substrate.

  According to the substrate polishing method of the present invention, even when the polishing rate measurement interval using the blank substrate exceeds a predetermined time, the transition of the polishing rate is stable, and the polishing parameter of the substrate based on the polishing rate is set. If the transition is stable, polishing is performed without performing test polishing using a blank substrate to calculate the polishing rate or test polishing using a pilot substrate extracted from the substrate to be polished to calculate polishing parameters. Because the substrate is polished using the predicted values of the polishing parameters based on the parameter history, the work throughput can be reduced and the substrate throughput can be improved without reducing the polishing accuracy, and the material cost can be reduced by omitting the test polishing. Can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<< First Embodiment >>
FIG. 2 is a diagram showing a system configuration example used in the CMP polishing process.

  FIG. 2 shows a system configuration example for polishing an interlayer insulating film of a semiconductor integrated circuit, and this system includes a polishing apparatus 10, a film thickness measuring apparatus 20, and a control apparatus 30. The polishing apparatus 10 is an apparatus for polishing a wafer, and the film thickness measuring apparatus 20 is an apparatus that optically measures the film thickness of the wafer, for example, so that the film thickness of the wafer can be measured before and after the polishing process. It has become. In addition, since the film thickness on the wiring cannot be measured on the wafer on which the wiring is formed, a flat monitor area is provided on the wafer, and the film thickness of the same monitor area is measured on all the wafers. To.

  The control device 30 is a device that controls the operations of the polishing device 10 and the film thickness measuring device. The control device 30 controls the control device 30 in an integrated manner, a storage unit 32 that stores various programs and data, the polishing device 10, and the like. A communication interface (I / F) 33 for performing data transmission / reception with the film thickness measurement device 20 and an input unit 34 for a user to input data are provided.

  For example, the user uses the input unit 34 of the control device 30 to input the lot number of the wafer to be polished and execute the polishing process. The control device 30 executes a predetermined program, calculates optimal polishing parameters based on the measurement result of the film thickness measuring device 20, and controls the polishing device 10. As will be described later, the control device 30 stores the history of the polishing parameters of the product wafer and the monitor wafer by the polishing device 10 as needed, and predicts the optimum parameters based on the tendency of those parameters. Thus, while maintaining the polishing accuracy, the number of test polishing using the pilot wafer and the monitor wafer of the product wafer is reduced, and the throughput of the polishing process is improved.

  The system for the polishing process includes, for example, a wafer transfer mechanism and a cleaning device in addition to the above configuration, and these operations may be controlled by the control device 30.

FIG. 3 is a diagram showing a schematic configuration example of the CMP polishing apparatus.
As shown in FIG. 3, the CMP polishing apparatus 10 is an apparatus for polishing an interlayer insulating film of a semiconductor integrated circuit. A wafer holder 12 for holding a wafer 11 to be polished and a platen 14 having a polishing pad 13 laid on the upper surface thereof. And a nozzle 15 for supplying the slurry and a dressing portion 16 for conspicuous the polishing pad 13.

  When polishing the wafer 11, the wafer 11 is attracted and held by the wafer holder 12 and pressed against the polishing pad 13. Then, the slurry from the nozzle 15 is supplied to the polishing pad 13 and the platen 14 and the wafer holder 12 are both rotated, whereby the entire surface of the wafer 11 is uniformly polished and flattened. Also, the dressing surface of the dressing portion 16 is pressed and rotated by the polishing pad 13, thereby conspicuous the surface of the polishing pad 13, preventing clogging of the polishing pad 13, and maintaining its polishing performance.

Next, the polishing process will be specifically described.
FIG. 4 is a diagram for explaining the relationship between the polishing time and the polishing amount.
The polishing process of the present embodiment includes a test polishing process using a monitor wafer in addition to the product wafer on which various patterns are formed. The monitor wafer is a so-called blank wafer in which a film material to be polished on the product wafer (here, an oxide film constituting an interlayer insulating film) is formed on a flat surface.

  In FIG. 4, the target polishing amount for the product wafer is the optimal polishing amount A_tr_pol, and the time required for polishing by this amount is the optimal polishing time T_tr_pol. As shown in FIG. 4, when the monitor wafer is polished, the polishing amount increases linearly in proportion to the polishing time. On the other hand, in the case of a product wafer, in the initial stage of polishing (polishing time is between 0 and T1), the convex part formed on the wiring pattern is polished, and the polishing rate of this part is higher than that of the flat part. Become fast. Since the flat portion is polished after T1 when the surface step is polished, the polishing rate is the same as that of the monitor wafer.

  The polishing rate at the initial stage of polishing is determined according to the layout of the wiring pattern and the amount of the interlayer insulating film formed. Therefore, in order to set the polishing time of the product wafer, the polishing time by the monitor wafer depends on the above conditions. It is necessary to give an offset. In the present embodiment, the polishing time (the polishing times T1 to T_tr_pol in the drawing) of the flat portion not including the convex portion on the upper surface of the product wafer is set as the initial value T_def_pol of the polishing time. In addition, the polishing amount when the polishing time initial value T_def_pol is polished from the upper end portion of the product wafer is defined as a polishing amount initial value A_def_pol.

  Then, after polishing from the upper end portion of the product wafer by the polishing time initial value T_def_pol, the polishing time or the polishing amount necessary for polishing the remainder is considered as the offset amount. That is, the polishing time required for the remaining polishing is an optimal polishing time offset T_tr_of, and the polishing amount is an optimal polishing amount offset A_tr_of.

Here, if the polishing rate (polishing amount / polishing time) of the monitor wafer is Rmn, the relationship of the following formulas (1) and (2) is established for the set value. As can be seen from these equations (1) and (2), for example, when the polishing rate Rmn of the monitor wafer is stable, it can be predicted that the optimum polishing amount offset A_tr_of is also stable. In other words, when the polishing rate Rmn varies linearly with the passage of time, polishing can be performed without degrading accuracy even if the optimum polishing amount offset A_tr_of is predicted and set based on the transition. Can be executed.
T_tr_pol = T_def_pol + T_tr_of (1)
T_tr_of = A_tr_of / Rmn (2)
FIG. 5 is a diagram for explaining parameters for polishing.

  The left side of FIG. 5 is a cross-sectional view of the product wafer. In the interlayer insulating film 111 to be polished by the CMP method, a convex portion 113 is formed on the lower layer (wiring layer) 112. In this example, a dishing portion 115 is formed on the Cu layer 114.

  In the polishing process of the interlayer insulating film 111 by the CMP polishing apparatus 10, the polishing amount offset initial value A_def_of is set as the initial value of the remaining polishing amount (offset amount) together with the above-described polishing amount initial value A_def_pol. The polishing amount offset initial value A_def_of is set to be smaller than the actually required polishing amount so that an amount larger than the target is not polished due to a polishing amount error. In the polishing process for a predetermined lot, based on the polishing amount offset initial value A_def_of, the optimum polishing amount offset A_tr_of is calculated based on the film thickness measurement result of the pilot wafer of the same lot or the product wafer that is actually polished. To go.

Assume that the measured thickness value (average value) of the entire product wafer after polishing is TH_af_pol, the target film thickness set in advance is TH_tg, and the polishing amount correction value (average value) for flattening the dishing portion 115 is A_dish. The optimum polishing amount offset A_tr_of is calculated by the following equation (3).
A_tr_of = A_def_of + TH_af_pol− (TH_tg + A_dish) (3)
In this embodiment, history information of the polishing rate Rmn of the monitor wafer and history information for each lot of the optimum polishing amount offset A_tr_of (or optimum polishing time offset T_tr_of) based on the film thickness measurement results of the product wafer and the pilot wafer are obtained. And stored in the storage unit 32 of the control device 30. If the value in the history information is stably changing, the predicted value is used as the offset amount to be set, and test polishing using a monitor wafer or a pilot wafer is omitted as appropriate. Thereby, the throughput of the product wafer is improved without reducing the polishing accuracy.

  FIG. 1 is a flowchart showing the overall flow of the CMP polishing process in the first embodiment. The following processing is performed by the CPU 31 of the control device 30 executing a processing program stored in the storage unit 32.

  [Step S101] The control device 30 receives a lot inquiry from the user through the input unit 34, searches the storage unit 32 in response to this, and searches for the corresponding polishing parameter and its history information.

  [Step S102] It is determined whether or not the polishing rate Rmn of the corresponding monitor wafer (blank wafer) on the day exists in the storage unit 32. If it exists, the process proceeds to Step S103. If not, the process proceeds to Step S103. The process proceeds to S105.

[Step S103] With reference to the history information of the polishing parameter of the product wafer (here, the optimum polishing amount offset A_tr_of), it is determined whether or not the transition of the polishing parameter is stable. For example, a primary approximation expression indicating the relationship between the optimum polishing amount offset A_tr_of and time is obtained, and a correlation value R1 between the optimum polishing amount offset A_tr_pf and a corresponding value on the first approximation expression is calculated. When (R1) ² exceeds 0.6, for example, it is determined that the transition is stable. If the transition is stable, the process proceeds to step S107. If the transition is not stable, the process proceeds to step S104.

[Step S104] With reference to the history information of the polishing parameter (optimum polishing amount offset A_tr_of), it is determined whether or not the correlation between the optimum polishing amount offset A_tr_of and the polishing rate Rmn (including the value of the current day) is high. For example, when the correlation value of these values is R2, it is determined that there is a correlation when (R2) ² exceeds 0.6. At this time, when history information of other apparatus parameters of the polishing apparatus 10 for polishing is also stored in the storage unit 32, the correlation between the fluctuation of the apparatus parameter and the fluctuation of the polishing rate Rmn is high. It may also be determined whether or not. If it is determined that all the correlations are high, the process proceeds to step S107. If not, the process proceeds to step S112.

[Step S105] With reference to the history information of the polishing rate Rmn, it is determined whether or not the transition of the polishing rate Rmn until the previous measurement is stable. For example, the correlation value R3 between the polishing rate Rmn and the corresponding value on the first-order approximate expression indicating the fluctuation of the polishing rate Rmn is calculated, and the transition is stable when (R3) ² exceeds 0.6, for example. It is determined that If the transition is stable, the process proceeds to step S106, and if not, the process proceeds to step S111.

  [Step S106] Similar to the processing in step S103, the history information of the polishing parameter (optimum polishing amount offset A_tr_of) is referred to and it is determined whether or not the transition of the offset amount is stable. If stable, the process proceeds to step S107, and if not stable, the process proceeds to step S112.

  [Step S107] Based on the linear approximation obtained from the history information of the polishing parameter (optimum polishing amount offset A_tr_of), a predicted value of the polishing parameter (optimum polishing amount offset A_tr_of) of the product wafer is calculated. For example, when the variation of the optimum polishing amount offset A_tr_of is approximated by a linear approximation expression as in this example, a value corresponding to the current time in the approximate line is set as the predicted value.

  [Step S108] The calculated polishing parameters are set in the polishing apparatus 10, the product wafer is transferred to the polishing apparatus 10, and the polishing process of the product wafer is executed. Before and after polishing, the film thickness measuring device 20 is used to measure the film thickness of the monitor region on the product wafer, and the control device 30 acquires the measured value.

  [Step S109] If the film thickness of the product wafer is the target value based on the measurement result of the film thickness, the process is terminated. In practice, for example, a predetermined number of product wafers are continuously polished based on the calculated polishing parameters. If the film thickness of the product wafer is not the target value, the process proceeds to step S110.

  [Step S110] For example, a polishing parameter for additional polishing is calculated using the latest polishing rate Rmn. Thereafter, the process returns to step S108, the product wafer is polished again, and the polishing is repeated until the target film thickness is reached.

  [Step S111] A test polishing process using a monitor wafer is performed. In this step, the monitor wafer (blank wafer) on which the same material as that for the polishing target portion of the product wafer is formed is polished, and the film thickness before and after polishing is measured. The control device 30 calculates the polishing rate Rmn from the film thickness measurement result and the polishing time, and stores it in the history information of the storage unit 32. By this test polishing process, a unique capability standard of the polishing apparatus 10 used for polishing is obtained. After executing this process, the process proceeds to step S112.

  [Step S112] A pilot wafer is selected from the product wafers, and a test polishing process using the pilot wafer is executed. This test polishing step is a step for obtaining an accurate polishing time under the same conditions as the polishing of the product wafer, and details thereof will be described later with reference to FIG. After executing the process, the process proceeds to step S108.

  In steps S103, S104, and S106 of the above steps, the optimum polishing amount offset A_tr_of is used as the offset amount. However, the optimum polishing time offset T_tr_of may be used instead.

FIG. 6 is a flowchart showing a flow of a test polishing process using a pilot wafer.
[Step S201] A pilot wafer is extracted from product wafers of a lot to be polished.

[Step S202] The pilot wafer polishing parameters are set in the polishing apparatus 10 and the set values are stored in the storage unit 32 of the control apparatus 30.
[Step S203] The pilot wafer is transferred to the polishing apparatus 10 and the polishing process of the pilot wafer is executed. Before and after polishing, the film thickness measuring device 20 is used to measure the film thickness of the monitor region on the pilot wafer, and the control device 30 acquires the measured value.

  [Step S204] If the film thickness of the pilot wafer is the target value based on the measurement result of the film thickness, the process proceeds to step S108 in FIG. 1 to start polishing the product wafer. At this time, the polishing parameter stored in step S202 (or subsequent step S205) is used as the polishing parameter of the product wafer. If the pilot wafer film thickness is not the target value, the process proceeds to step S205.

  [Step S205] For example, the latest polishing rate Rmn is used to calculate polishing parameters for additional polishing, and the polishing parameters stored in the storage unit 32 in step S202 are updated. Thereafter, the process returns to step S203 to polish the pilot wafer again, and the polishing is repeated until the target film thickness is reached.

Here, FIG. 7 is a graph showing an example of transition of the polishing rate Rmn.
In FIG. 7, an approximate straight line is calculated using a first-order approximation formula based on a measurement value when the polishing rate Rmn is measured every other day within a predetermined period as an example, and this approximation formula and each measurement value are calculated. The correlation value R3 is calculated. When this correlation value is high, that is, when the measured value is close to the approximate line, it can be determined that the transition of the polishing rate Rmn is stable, and the predicted value of the next polishing rate Rmn is taken from the extended line of the approximate line. Can do. In the example of FIG. 7, (R3) ² = 0.2706 is calculated, and when (R3) ² > 0.6 is used as a stability criterion, it is determined that the transition is not stable.

FIG. 8 is a graph showing an example of transition of the optimum polishing time offset T_tr_of.
In FIG. 8, a first-order approximation formula based on a measured value when the optimum polishing time offset T_tr_of is measured every other day within a predetermined period as an example, and a correlation value R1 between the measured values are calculated. When this correlation value is high, that is, when the measured value is close to the approximate line, it can be determined that the transition of the optimum polishing time offset T_tr_of is stable as in the case of the polishing rate Rmn. The predicted value of the optimum polishing time offset T_tr_of can be taken. In the example of FIG. 8, (R1) ² = 0.0048 is calculated, and when (R1) ² > 0.6 is used as a stability criterion, it is determined that the transition is not stable.

In the above processing example, the primary approximate expression is used for calculating the correlation value, but the present invention is not limited to this, and other approximate expressions may be used.
In the CMP polishing step described above, when the polishing rate Rmn using the monitor wafer has been measured even once that day, the offset amount (that is, the optimal polishing amount offset A_tr_of or the optimal polishing time offset T_tr_of) is set. If the transition is stable, the product wafer is polished using the predicted value calculated from the offset amount transition without performing test polishing using the pilot wafer again (steps S102, S103, S107).

  Even if the transition of the offset amount is not stable, if the correlation between the offset amount and the polishing rate Rmn is high, the variation in the offset amount is caused by the variation in the state of the polishing apparatus 10, and the other Since it is considered that there is a high possibility that it is not caused by a cause, the product wafer is polished by predicting the offset amount without performing the test polishing using the pilot wafer (steps S102 to S104, S107).

  On the other hand, even when the measurement of the polishing rate Rmn using the monitor wafer is not performed once in the day, the transition of the polishing rate Rmn until the previous measurement is stable and the transition of the offset amount is also stable. In this case, the product wafer is polished using the predicted value calculated from the transition of the offset amount without performing the test polishing using the monitor wafer or the test polishing using the pilot wafer (steps S102, S105 to S107).

  In this way, it is determined whether or not test polishing using a monitor wafer or a pilot wafer is necessary according to the change in the polishing rate Rmn and the offset amount, and these test polishings are omitted as appropriate, thereby reducing the polishing accuracy. In addition, the number of executions of test polishing can be reduced as compared with the prior art, the process can be made more efficient, and the throughput of the product wafer can be improved. The number of monitor wafers and pilot wafers can be reduced, and the slurry used for the test polishing is not necessary, so that the manufacturing cost can be reduced.

  It is desirable that the polishing rate Rmn using the monitor wafer is periodically measured within a certain period. For example, the period during which measurement is omitted is about 7 days at maximum. Further, when the transition of the polishing rate Rmn is stable, the number of days for which measurement is omitted may be gradually extended.

  FIG. 9 is a flowchart showing a processing example when the number of days for omitting the measurement of the polishing rate Rmn is gradually extended. This flowchart replaces the process of step S105 in FIG.

  [Step S301] In step S102 of FIG. 1, if the polishing rate Rmn of the current day is not stored in the storage unit 32, the history information of the polishing rate Rmn is first referred to, and the transition of the polishing rate Rmn up to the previous measurement time. It is determined whether or not is stable. If stable, the process proceeds to step S303, and if not stable, the process proceeds to step S302.

[Step S302] The variable N stored in the storage unit 32 is set to 0, and then the process proceeds to step S111 in FIG. 1 to perform test polishing using the monitor wafer.
[Step S303] When the polishing rate Rmn is stable, the number of days in which measurement is omitted, that is, the polishing rate Rmn is finally determined, which is obtained from the current variable N and the history information of the polishing rate Rmn by subsequent processing. Process according to the number of days that have elapsed since the measurement. In step S303, when the variable N is 0, it progresses to step S304, and when that is not right, it progresses to step S306.

  [Step S304] If the number of omitted days is less than 1, the process proceeds to Step S305. If it is 1, the process proceeds to step S107 in FIG. 1, and the predicted value of the polishing parameter is calculated and polishing of the product wafer is performed without performing the test polishing using the monitor wafer and the pilot wafer.

[Step S305] 1 is added to the variable N, and the process proceeds to step S111 to perform test polishing using a monitor wafer.
[Step S306] If the variable N is 1, the process proceeds to step S307. Otherwise, the process proceeds to step S308.

  [Step S307] If the number of omitted days is less than 2, the process proceeds to Step S305. If it is 2, the process proceeds to step S107 in FIG. 1, and a predicted value of the polishing parameter is calculated to polish the product wafer.

[Step S308] If the variable N is 2, the process proceeds to step S309. Otherwise, the process proceeds to step S310.
[Step S309] If the number of omitted days is less than 4, the process proceeds to Step S305. If it is 4, the process proceeds to step S107 in FIG. 1, and a predicted value of the polishing parameter is calculated to polish the product wafer.

  [Step S310] If the number of days omitted is less than 7, the variable N is not added, and the process proceeds to Step S111 to perform test polishing using the monitor wafer. If the number of omitted days is 7, the process proceeds to step S107 in FIG. 1, and the predicted value of the polishing parameter is calculated to polish the product wafer.

  According to the above process, when the change in the polishing rate Rmn is stable, the test polishing using the monitor wafer is executed at intervals of every other day, every second day, every fourth day, every seventh day. Thus, the throughput of the product wafer can be improved by reducing the number of executions of the test polishing without lowering the polishing accuracy without increasing the polishing accuracy.

<< Second Embodiment >>
By the way, in the first embodiment described above, the error in the polishing accuracy due to the state of the polishing apparatus including the consumables such as the polishing pad, the slurry, and the dressing portion is canceled by the polishing rate Rmn of the monitor wafer. By stabilizing this polishing rate Rmn, it is possible to extend the measurement cycle of the polishing rate Rmn and reduce the work man-hours and material costs.

  As parameters affecting the polishing rate Rmn, the pressure for pressing the wafer against the polishing pad, the number of rotations of the platen or the wafer holder, the temperature at the time of polishing, and the like can be considered. Of these, the temperature can be controlled to some extent by flowing a temperature-controllable coolant through the platen, but the reaction of the temperature control is slow, and the polishing pad that is actually being polished is in contact with the wafer. It is difficult to control the temperature of the part where it is. Therefore, in the present embodiment, for example, the temperature of the surface of the polishing pad is monitored using an infrared temperature sensor, and the polishing rate Rmn is controlled by controlling the pressure or rotation speed of the wafer so that the temperature becomes appropriate. Stabilize.

FIG. 10 is a diagram illustrating a system configuration example according to the second embodiment.
In the system shown in FIG. 10, an infrared temperature sensor 40 is provided in the configuration shown in FIG. The infrared temperature sensor 40 measures the temperature of the surface of the polishing pad and outputs temperature information to the control device 30 through the communication I / F 33. The CPU 31 of the control device 30 controls the pressure on the wafer placed on the polishing device 10 or the number of rotations of the polishing pad and the wafer holder according to the temperature information from the infrared temperature sensor 40.

  FIG. 11 is a flowchart showing the flow of a test polishing process using a monitor wafer. The process of FIG. 11 replaces the process of step S111 of FIG. Further, although this flowchart shows an example in which the pressure for pressing the wafer is changed, the rotational speed may be increased or decreased instead of increasing or decreasing the pressure.

  In this process, the upper and lower limits of the optimum temperature for the monitor wafer are set to Hmax and Hmin, respectively. First, the monitor wafer polishing parameters are set in the polishing apparatus 10, and the set values are stored in the storage unit 32 of the control apparatus 30 (step S401). Next, the monitor wafer is transferred to the polishing apparatus 10 and the polishing process for the monitor wafer is started (step S402). Before the polishing, the film thickness measuring device 20 is used to measure the film thickness of the monitor region on the monitor wafer, and the control device 30 stores the measured value.

  During polishing, temperature information from the infrared temperature sensor 40 is acquired as needed. When the detected temperature H detected by the infrared temperature sensor 40 exceeds Hmax (step S403), the pressure for pressing the monitor wafer is reduced (step S404). If the detected temperature H is lower than Hmin (step S405), the pressure is increased (step S406). Such control according to the temperature is repeated until the set time elapses (step S407), and when the set time elapses, the film thickness measuring device 20 is made to measure the film thickness of the monitor wafer, and the target film thickness is reached. In the case where the test polishing process is completed (step S408), if the target film thickness is not reached, the polishing parameter for additional polishing is calculated using the latest polishing rate Rmn, and the step is performed. The polishing parameters stored in the storage unit 32 in S401 are updated (step S409). Thereafter, the process returns to step S402 to polish the monitor wafer again, and the polishing is repeated until the target film thickness is reached.

  Through the above steps, the surface of the polishing pad is maintained at a temperature in a substantially constant range, so that polishing errors due to temperature fluctuations are eliminated, and the transition of the polishing rate Rmn is more stabilized. Accordingly, the number of times the polishing rate is measured is reduced, and the throughput of the product wafer can be improved and the manufacturing cost can be reduced without reducing the polishing accuracy.

  In each of the above embodiments, the case where the present invention is applied to a semiconductor wafer polishing process has been described. In addition to this, for example, a magnetic disk manufacturing process, a multichip module manufacturing process using a ceramic substrate, Even when applied to a polishing process in a manufacturing process of a glass substrate for display such as liquid crystal or for a photomask, the substrate to be polished can be polished with high accuracy and its throughput can be improved.

(Appendix 1) In a substrate polishing method for polishing a substrate surface by a CMP method,
A first determination step of determining whether the polishing rate measurement interval exceeds the time using a blank substrate on which the same film material as that to be polished is formed;
A second determination step of determining abnormality of the polishing rate based on the measurement history of the polishing rate;
A third determination step of determining an abnormality in a history of polishing parameters based on the polishing rate for polishing the substrate to a predetermined thickness;
A predicted value calculating step of calculating a predicted value of the polishing parameter based on the history of the polishing parameter;
A polishing step of polishing the substrate by CMP using the predicted value;
A substrate polishing method comprising:

  (Supplementary Note 2) In the second determination step, an approximate expression that approximates the transition of the polishing rate is calculated, and based on a correlation value between a past measurement value of the polishing rate and a corresponding value on the approximate expression. 2. The substrate polishing method according to appendix 1, wherein it is determined whether or not the transition of the polishing rate is stable.

  (Supplementary Note 3) When it is determined in the second determination step that the polishing rate is abnormal, a polishing rate calculation step of performing a test polishing using the blank substrate and calculating the current polishing rate is executed. The method of polishing a substrate according to appendix 1, wherein:

  (Supplementary Note 4) After the polishing rate calculating step, further using the calculated polishing rate, polishing a pilot substrate extracted from the substrate to be polished, and further executing a polishing parameter calculating step of calculating the polishing parameter The substrate polishing method according to supplementary note 3, characterized by:

  (Additional remark 5) In the said polishing rate calculation step, according to the temperature of the polishing pad which grind | polishes the said blank substrate, the pressure with respect to the said polishing pad of the said blank substrate, or the rotation speed of at least one of the said polishing pad and the said blank substrate The method of polishing a substrate according to supplementary note 3, wherein: is corrected.

  (Additional remark 6) Even if it determines with the said polishing rate being normal at the said 2nd determination step, when the said polishing rate is not measured for a fixed period, test polishing using the said blank substrate is performed. 2. The substrate polishing method according to appendix 1, wherein a polishing rate calculation step of calculating the current polishing rate is executed.

  (Additional remark 7) When it is continuously determined that the said polishing rate is normal in the said 2nd determination step, the space | interval which performs the said polishing rate calculation step is gradually lengthened, The additional remark 6 characterized by the above-mentioned. Substrate polishing method.

  (Supplementary Note 8) In the third determination step, an approximate expression that approximates the transition of the polishing parameter is calculated, and based on a correlation value between a past value of the polishing parameter and a corresponding value on the approximate expression, The substrate polishing method according to appendix 1, wherein it is determined whether or not the transition of the polishing parameter is stable.

  (Supplementary Note 9) When it is determined in the third determination step that the history of the polishing parameter is abnormal, the polishing parameter is calculated by performing test polishing using a pilot substrate extracted from the substrate to be polished. The substrate polishing method according to appendix 1, wherein a polishing parameter calculation step is executed.

  (Supplementary Note 10) In the first determination step, when the polishing rate has been measured within a predetermined period in the past, a fourth determination step is performed to determine abnormality of the history of the polishing parameter, and the polishing is performed. The substrate polishing method according to appendix 1, wherein the predicted value calculation step is executed when it is determined that the parameter history is normal.

  (Supplementary Note 11) In the fourth determination step, an approximate expression that approximates the transition of the polishing parameter is calculated, and based on a correlation value between a past value of the polishing parameter and a corresponding value on the approximate expression, The substrate polishing method according to appendix 10, wherein it is determined whether or not the transition of the polishing parameter is stable.

  (Supplementary Note 12) When it is determined in the fourth determination step that the history of the polishing parameter is abnormal, the transition of the polishing parameter is referred to with reference to the history of the polishing parameter and the history of the polishing rate. 11. The substrate polishing according to claim 10, wherein a fifth determination step for determining whether or not the correlation with the transition of the polishing rate is high is executed, and the predicted value calculation step is executed when the correlation is high. Method.

  (Supplementary Note 13) In the fifth determination step, when the correlation between the transition of the polishing parameter and the transition of the polishing rate is low, test polishing is performed using a pilot substrate extracted from the substrate to be polished. 13. The substrate polishing method according to appendix 12, wherein a polishing parameter calculation step for calculating a polishing parameter is executed.

  (Supplementary note 14) The substrate according to supplementary note 1, wherein, in the predicted value calculating step, a value corresponding to the current time is calculated as the predicted value in a straight line or curve by an approximate expression approximating the transition of the polishing parameter. Polishing method.

It is a flowchart which shows the whole flow of the CMP grinding | polishing process in 1st Embodiment. It is a figure which shows the system structural example used for a CMP grinding | polishing process. It is a figure which shows the schematic structural example of CMP polishing apparatus. It is a figure for demonstrating the relationship between grinding | polishing time and grinding | polishing amount. It is a figure for demonstrating the parameter for grinding | polishing. It is a flowchart which shows the flow of the test grinding | polishing process using a pilot wafer. It is a graph which shows the example of transition of a polishing rate. It is a graph which shows the example of transition of optimal polishing time offset. It is a flowchart which shows the process example in the case of extending the days which abbreviate | omit the measurement of a polishing rate gradually. It is a figure which shows the system configuration example which concerns on 2nd Embodiment. It is a flowchart which shows the flow of the test grinding | polishing process using a monitor wafer. It is a flowchart which shows an example of the grinding | polishing procedure of the conventional semiconductor wafer by CMP method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polishing apparatus 11 Wafer 12 Wafer holder 13 Polishing pad 14 Platen 15 Nozzle 16 Dressing part 20 Film thickness measuring apparatus 30 Control apparatus 31 CPU
32 storage unit 33 communication I / F
34 Input section

Claims (3)

In a substrate polishing method for polishing a substrate surface by a CMP method,
A first determination step of determining whether the polishing rate measurement interval exceeds the time using a blank substrate on which the same film material as that to be polished is formed;
When it is determined that the polishing rate has not been measured for a predetermined time, a first approximate expression that approximates the transition of the polishing rate is calculated based on the measurement history of the polishing rate, and the past measurement of the polishing rate is calculated. A second determination step of determining whether or not the transition of the polishing rate is stable based on a correlation value between a value and a corresponding value on the first approximate expression;
When it is determined that the transition of the polishing rate is stable, the polishing parameter A second approximate expression approximating the transition is calculated, and whether the transition of the polishing parameter is stable based on the correlation value between the past value of the polishing parameter and the corresponding value on the second approximate expression A third determination step for determining whether or not;
When it is determined that the transition of the polishing parameter is stable, a value corresponding to the current time in a straight line or a curve by an approximate expression approximating the transition of the polishing parameter is calculated as a predicted value of the polishing parameter. A predicted value calculating step;
A polishing step of polishing the substrate by CMP using the predicted value;
A substrate polishing method comprising: In the first determination step, when the polishing rate has been measured within a predetermined period in the past, a third approximate expression that approximates the transition of the polishing parameter is calculated based on the history of the polishing parameter, Based on a correlation value between a past value of the polishing parameter and a corresponding value on the third approximate expression, a fourth determination step is performed to determine whether or not the transition of the polishing parameter is stable. 2. The substrate polishing method according to claim 1, wherein when the transition of the polishing parameter is determined to be stable, the predicted value calculation step is executed. When it is determined in the fourth determination step that the transition of the polishing parameter is not stable, the polishing parameter transition and the polishing rate are referred to with reference to the polishing parameter history and the polishing rate history. A fifth determination step is performed to determine whether a value based on a correlation value with the transition of the value exceeds a predetermined threshold value, and when the value based on the correlation value exceeds the predetermined threshold value, The substrate polishing method according to claim 2, wherein a predicted value calculation step is executed.

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